Focusing on the accumulation of chromatin/chromosomes around nucleoli and optimizing the timing of ICSI to facilitate the rescue in vitro maturation of denuded GV stage oocytes.

Abstract

This study aims to achieve the methodological improvement of rescue IVM by predicting germinal vesicle breakdown (GVBD) and optimizing the timing of ICSI. Time lapse analysis was performed retrospectively to evaluated the relationship between the presence of AC around the nucleoli and GVBD. To find the optimal timing of ICSI, the time from the initiation of the first polar body extrusion to ICSI were measured, and the rates of fertilization at each point were calculated. The GVBD rate of GV stage oocytes with AC around the nucleoli was significantly higher than that of GV stage oocytes without AC. The GV stageoocytes required more time for nuclear maturation after polar body extrusion than MI oocytes, with GV stageoocytes taking 400-600min from polar body extrusion to the optimal timing of ICSI, while the MI stageoocytes took 200-400min. The GV stage oocytes resulted in the birth of healthy babies with the appropriate timing of ICSI. It was found that GV stageoocytes with AC around nucleoli can initiate GVBD and reach the MII stage with a high rate, and that GV stage oocytes required more time than MI stageoocytes to reach the optimal timing of ICSI. Considering these factors, ART laboratories may employ immature GV stageoocytes in routine ART procedures rather than discarding them.